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Fri, 18 Sep 2026 07:21:19 -0700 (PDT) Received: from x1c ([2405:9800:b670:b64b:f2cd:1bf9:a704:c687]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-39e3617443asm13420739a91.9.2026.09.18.07.21.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 18 Sep 2026 07:21:18 -0700 (PDT) From: Tharit Tangkijwanichakul To: Paolo Bonzini , Shuah Khan Cc: Sean Christopherson , kvm@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kernel-mentees@lists.linux.dev, skhan@linuxfoundation.org, me@brighamcampbell.com, jkoolstra@xs4all.nl, Tharit Tangkijwanichakul Subject: [PATCH v2] KVM: selftests: Test partial KVM_CLEAR_DIRTY_LOG requests Date: Fri, 18 Sep 2026 21:20:52 +0700 Message-ID: <20260918142053.10127-1-tharitt97@gmail.com> X-Mailer: git-send-email 2.53.0 Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit The clear-log mode invokes KVM_CLEAR_DIRTY_LOG with first_page set to zero and num_pages covering the entire memory slot. But the clear-log allows targeted clearing. So, the test does not verify that KVM correctly applies a bitmap relative to a nonzero first_page, or that pages not selected by a partial request remain dirty. Add a focused test that creates a memory slot with KVM_DIRTY_LOG_INITIALLY_SET, then submits a 64-page clear request starting at page 64 with only bitmap bit 1 set. Verify that memslot page 65 becomes clean while every other host-page bit remains dirty. Write to page 65 from the guest and verify that dirty tracking was re-enabled and the page becomes dirty again. Signed-off-by: Tharit Tangkijwanichakul --- Changes in v2: Address two issues from Sashiko's review - Address Out-of-bound guest access when host page size exceeds the guest page size by sizing the test memslot from 192 host pages, converting to guest pages before applying the allocation adjustment. - Skip the partial-clear test if KVM_DIRTY_LOG_INITIALLY_SET is not supported, since the test requires the bitmap to start with all pages marked dirty. Test Results: - on x86_64 with 4K host and guest pages: ./dirty_log_test -M clear-log PASS - on arm64 Rock 5B with 4K host pages, including 4K, 16K and 64K guest page modes: ./dirty_log_test -M clear-log PASS --- tools/testing/selftests/kvm/dirty_log_test.c | 112 +++++++++++++++++++ 1 file changed, 112 insertions(+) diff --git a/tools/testing/selftests/kvm/dirty_log_test.c b/tools/testing/selftests/kvm/dirty_log_test.c index af5eb0334a74..3976748f3940 100644 --- a/tools/testing/selftests/kvm/dirty_log_test.c +++ b/tools/testing/selftests/kvm/dirty_log_test.c @@ -815,6 +815,114 @@ static void run_test(enum vm_guest_mode mode, void *arg) kvm_vm_free(vm); } +/* Use the 2nd 64-page range to exercise a non-zero offset. */ +#define TEST_CLEAR_LOG_FIRST_PAGE 64 +#define TEST_CLEAR_LOG_NUM_PAGES 64 +#define TEST_CLEAR_LOG_BIT 1 +#define TEST_CLEAR_LOG_PAGE (TEST_CLEAR_LOG_FIRST_PAGE + \ + TEST_CLEAR_LOG_BIT) +static void guest_code_clear_log(void) +{ + u64 addr = guest_test_virt_mem + TEST_CLEAR_LOG_PAGE * host_page_size; + + while (true) { + vcpu_arch_put_guest(*(u64 *)addr, 1); + GUEST_SYNC(1); + } +} + +/* + * Verify KVM_CLEAR_DIRTY_LOG only clears (and re-arms) the requested range: + * with KVM_DIRTY_LOG_INITIALLY_SET every page starts dirty; clearing a single + * page must leave its neighbours dirty and must write-protect the page so the + * next guest write re-dirties it. + */ +static void run_clear_log_partial_test(enum vm_guest_mode mode, void *arg) +{ + unsigned long *bmap, *clear_bmap; + struct kvm_vcpu *vcpu; + struct kvm_vm *vm; + u64 page; + + /* Allocate enough memory for three 64-host-page range */ + guest_num_pages = vm_adjust_num_guest_pages(mode, + vm_num_guest_pages(mode, 3 * 64)); + + vm = create_vm(mode, &vcpu, 2 * guest_num_pages, guest_code_clear_log); + + guest_page_size = vm->page_size; + host_num_pages = vm_num_host_pages(mode, guest_num_pages); + host_page_size = getpagesize(); + + guest_test_virt_mem = DEFAULT_GUEST_TEST_MEM; + guest_test_phys_mem = (vm->max_gfn - guest_num_pages) * guest_page_size; + guest_test_phys_mem = align_down(guest_test_phys_mem, host_page_size); + + bmap = bitmap_zalloc(host_num_pages); + clear_bmap = bitmap_zalloc(BITS_PER_LONG); + + vm_userspace_mem_region_add(vm, VM_MEM_SRC_ANONYMOUS, + guest_test_phys_mem, TEST_MEM_SLOT_INDEX, + guest_num_pages, KVM_MEM_LOG_DIRTY_PAGES); + virt_map(vm, guest_test_virt_mem, guest_test_phys_mem, guest_num_pages); + + sync_global_to_guest(vm, host_page_size); + sync_global_to_guest(vm, guest_test_virt_mem); + + kvm_vm_get_dirty_log(vm, TEST_MEM_SLOT_INDEX, bmap); + for (page = 0; page < host_num_pages; page++) + TEST_ASSERT(test_bit_le(page, bmap), + "Page %lu should be dirty after INITIALLY_SET", page); + + __set_bit_le(TEST_CLEAR_LOG_BIT, clear_bmap); + kvm_vm_clear_dirty_log(vm, TEST_MEM_SLOT_INDEX, clear_bmap, + TEST_CLEAR_LOG_FIRST_PAGE, + TEST_CLEAR_LOG_NUM_PAGES); + + kvm_vm_get_dirty_log(vm, TEST_MEM_SLOT_INDEX, bmap); + for (page = 0; page < host_num_pages; page++) { + if (page == TEST_CLEAR_LOG_PAGE) + TEST_ASSERT(!test_bit_le(page, bmap), + "Cleared page %lu should be clean", page); + else + TEST_ASSERT(test_bit_le(page, bmap), + "Page %lu should still be dirty", page); + } + + /* The cleared page is now write-protected; a guest write must re-arm it */ + vcpu_run(vcpu); + TEST_ASSERT(get_ucall(vcpu, NULL) == UCALL_SYNC, + "Unexpected guest exit: %s", + exit_reason_str(vcpu->run->exit_reason)); + + kvm_vm_get_dirty_log(vm, TEST_MEM_SLOT_INDEX, bmap); + TEST_ASSERT(test_bit_le(TEST_CLEAR_LOG_PAGE, bmap), + "Page %lu should be dirty again after re-arming", + (u64)TEST_CLEAR_LOG_PAGE); + + free(bmap); + free(clear_bmap); + kvm_vm_free(vm); +} + +static void test_clear_log_partial(void) +{ + host_log_mode = LOG_MODE_CLEAR_LOG; + if (!log_mode_supported()) { + print_skip("Log mode '%s' not supported", + log_modes[host_log_mode].name); + return; + } + + if (!(kvm_check_cap(KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2) & + KVM_DIRTY_LOG_INITIALLY_SET)) { + print_skip("KVM_DIRTY_LOG_INITIALLY_SET not supported"); + return; + } + + for_each_guest_mode(run_clear_log_partial_test, NULL); +} + static void help(char *name) { puts(""); @@ -913,5 +1021,9 @@ int main(int argc, char *argv[]) for_each_guest_mode(run_test, &p); } + if (host_log_mode_option == LOG_MODE_ALL || + host_log_mode_option == LOG_MODE_CLEAR_LOG) + test_clear_log_partial(); + return 0; } -- 2.53.0